a. Field of the Invention
The present invention relates to a radio telephone set or a radio telephone set provided with broadcast receiving functions as well as radio telephone functions and, more specifically, to a radio telephone set in which the way of ring output at the time of a call termination and the way of supplying electric power at the time is adapted for the functions.
b. Description of the Prior Art
A variety of portable telephone sets have been developed and are commercially available so far. However, they are provided with only telephone functions. There have not yet been developed such an article into which a telephone and a radio set have been combined. Since tuner circuits for radio sets etc. have been developed which are very small in size, it is possible to include such tuner circuit in portable telephone sets without changing their size or weight, thereby advantageously permitting such portable telephone sets to be used also as portable radio sets.
However, in a system into which a tuner circuit for radio and a telephone circuit have been simply combined as described above, when a call is terminated while the user is listening to the radio through the headset, he or she may miss the alerting tone informing of the termination, preventing the telephone function from working.
Also, in a portable telephone set, which uses a chargeable battery or an electric cell as a power supply, the power consumption has to be held down to prolong the available time period. For this purpose, the power is saved in a wait state by means of intermittent receiving operation in which the power supply is switched on and off alternately. In this case, noises of the power supply may affect the tuner section during a power supply burst operation, possibly deteriorating the quality of the received audio signal.